Cranial Nerves Review 234

Cranial NervesCN I Olfactory

Exits cranial cavity through cribiform plate of ethmoidal bone Olfactory bulb- sense of smell

CN II Optic Through optic canal with ophthalmic artery

CN III Occulomotor Exits cranial cavity through superior orbital fissure Parasympathetic

o CN III synapses in ciliary ganglion-> runs with long ciliary (branch of nasociliary from CN V1) and short ciliary nerves (branch of ciliary ganglion)

o Targets constrictor pupillae and ciliary muscles Sympathetic

o Synapse in superior cervical ganglion-> travels with ophthalmic artery to dilator pupillae

Motor innervation to levator palpebrae superioris and superior rectus

CN IV Trochlear Exits cranial cavity through superior orbital fissure Innervates superior oblique

CN V Trigeminal 1. Opthalmic Division Nerve- exits through superior orbital fissure

a. Nasociliary nervei. Anterior and posterior ethmoidal

1. Anteriosuperior portion of nasal cavityii. Long ciliary nerve- runs with CN III to pupillae and ciliary muscles

iii. Sensory root of ciliary ganglionb. Frontal nerve

i. Supratrochlearii. Supraorbital

c. Lacrimal nerve

2. Maxillary Division Nerve- exits through foramen rotunduma. Infraorbital nerve through infraorbital foramenb. Zygomatic nerve through inferior orbital fissurec. Nasaopalatine nerve- posteroinferior part of nasal cavityd. Lesser palatine nerve- sensory innervation of soft palate

3. Mandibular Division Nerve- exits through foramen ovalea. Sensory Branches

i. Auriculo-temporal- to auricle and temporal regions, TMJ, postganglionc parasympathetic to parotid gland

ii. Inferior Alveolar- enters mandibular foramen to supplies teeth, lower lip, chin

iii. Lingual- general sense to anterior 2/3 of tongueiv. Buccal- sense to skin and oral mucosa of cheek and gingivae

b. Motor Branchesi. To muscles of mastication, tensor tympani (malleus), tensor pallatini

(soft palate), anterior belly of digastric, mylohyoidCN VI Abducent

- Runs with lateral rectus-

CN VII Facial 5-6 Superficial Branches:

o Posterior auricularo Temporalo Zygomatico Buccalo Mandibularo Cervical

Chorda tympanio Exits skull through internal acoustic meatus, travels through middle ear

between malleus and incus, through petrotympanic fissure to infratemporal fossa

o Parasympathetic fibers to submandibular and sublingual glandso Special taste sense to anterior 2/3 tongueo Joins lingual nerve to submandibular ganglion

Pathway: Exits cranial cavity through internal acoustic meatuso Forms geniculate gangliono Gives off greater petrosal nerve (parasympathetic fibers to lingual, nasal

and palatine glands- synapse in pterygopalatine ganglion, taste to palate)o Through facial canal, gives off motor branches to stapediuso Branches to chorda tympani (parasympathetic fibers to sublingual and

submandibular glands- synapse in submandibular ganglion, taste to tongue)o Branches to external acoustic meatuso Exits through stylomastoid foramen

Greater petrosal (parasympathetic) and deep petrosal (sympathetic from carotid plexus, with internal carotid artery) travel partly through foramen lacerum and combine in pterygoid canal to form nerve of pterygoid canal

CN VIII Vestibulocochlear Hearing and balance sense- inner ear Pathway: exits cranial cavity through internal acoustic meatus, to cochlea,

semicircular canals, saccule, utricle

CN IX Glossopharyngeal Pathway: exits cranial cavity through jugular foramen, re-enters as tympanic

nerve, tympanic nerve forms tympanic plexus in medial wall of middle ear, gives off lesser petrosal nerve-> leaves middle ear anteriorly

Sympathetics: Caroticotympanic nerve travels from internal carotid plexus to tympanic plexus with lesser petrosal nerve

Lesser petrosal and caroticotympanic nerve from tympanic plexus, innervate parotid gland and synapse in otic ganglion

Travels with stylopharyngeus muscle in posterior neck o Can also be seen passing under hyoglossus to tonsilar bed between

palatoglossal arch and palatopharyngeal arch in mouth

CN X Vagus Exits cranial cavity through jugular foramen, passes into carotid sheath Motor supply to muscles of pharynx (except for stylopharyngeus-CN IX) Branches:

o Recurrent laryngealo Superior laryngeal divides into-> external and internal laryngealo Pharyngeal- motor nerve of pharynx and palate

Pharyngeal branch of Glossopharyngeal- sensory (IX), Pharyngeal branch of Vagus- motor (X) form pharyngeal plexus-> branches to muscles of pharynx

CN XI Accessory Enters skull through foramen magnum and exits through jugular foramen (with CN

IX and X) Motor innervation to trapezius and sternocleidomastoid

CN XII Hypoglossal Exits cranial cavity through hypoglossal canal on side of foramen magnum Runs along underside of jaw Innervates muscles of tongue Superior portion of ansa cervicalis runs with hypoglossal

Palate Nerves- V2 (maxillary branch of trigemincal) gives off nasopalatine nerve

o Enters nasal cavity through sphenopalatine foramen, travels through septum and enters palate through incisive canal

- Greater palatineo Branch of pterygopalatine gangliono Emerges to palate through greater palatine foramen

- Lesser palatine o Branch of pterygopalatine gangliono Emerges to palate through lesser palatine foramen

Tongue- General sensation

o Ant 2/3: lingual of V3o Post 1/3: CN IX

- Special sense of tasteo Ant 2/3: chorda tympani of VII facialo Post 1/3: CN IX

ArteriesNasal

- Anterior ethmoidal and posterior ethmoidalo Via ophthalmic

- Sphenopalatine artery and greater palatine arteryo Via maxillary

- Septal branch of superior labial arteryo Via facial artery

- Nasal branches anastomose to make Kiesselbach’s area

SUBCLAVIAN ARTERY: median -> lateral Vertebral artery (up) Internal thoracic (down) Thryocervical trunk: before anterior scalene

o Inferior thyroid (up-ascending cervical artery off of inferior thyroid)o Transverse cervical (across- above suprascapular)o Suprascapular (across- parallel with clavicle/subclavius muscle)

Costocervical trunk: behind anterior scaleneo Deep cervical (runs up back of neck)o Superior intercostal

Dorsal scapular artery (variation: branch of either subclavian or transverse cervical)o Runs down medial side of scapula

EXTERNAL CAROTID ARTERY Carotid triangle:

o Superior thyroid (anterior)o Ascending pharyngeal (posterior- straight up from back of external carotid-

runs btwn internal and external)o Lingual (anterior)o Facial (anterior)

Ascending palatine (to palate) Tonsillar (to palate) Glandular Submental Facial branches: Inferior labial, superior labial (nose), lateral nasal,

angular, muscularo Occipital (posterior to back of head)

Posterior Auricular (posterior- behind ear) Terminal branches: Maxillary (to midface), Superficial temporal (near temporal

bone) Some Anatomists Like Freaking Out Poor Med Students

o Superior thyroid, Ascending Pharyngeal, Facial, Lingual, Occipital, Posterior auricular, Maxillary, Superficial temporal

MAXILLARY ARTERY (off of external carotid)Infratemporal Fossa

- External carotid-> Maxillary: o 1st part

Inferior alveolar (going downwards to mandibular foramen) Branch: Mylohyoid

Middle meningeal (going upwards-enters through foramen spinosum),

o 2nd part Deep temporal branches (upwards) Buccal (side)

o 3rd part Posterior Superior Alveolar Infraorbital (in infraorbital fissure) Sphenopalatine (in pterygopalatine fossa)

o I’m Deeply Buccled-PIS Inferior Alveolar, Middle meningeal, Deep temporal, Buccal, Posterior

superior alveolar, Infraorbital, Sphenopalatine

INTERNAL CAROTID- Opthalmic artery

o Central retinal (small, runs inferior to optic nerve) o Lacrimal (large, runs to lacrimal gland along lateral rectus)o Posterior ciliary

Long and short ciliary arterieso Supraorbitalo Supratrochlearo Posterior ethmoidal (go medial to nasal cavity)o Anterior ethmoidal (go medial to nasal cavity)o Dorsal nasal

Palate- Maxillary gives off descending palatine (from 3rd part)-> branches to greater and

lesser palatine- Facial (ext. carotid) gives off Ascending palatine artery- Lingual (ext. carotid) gives off Tonsilar artery - Ascending pharyngeal (ext. carotid) gives off palatine branch- Anastomoses with Sphenopalatine (maxillary)

MusclesInfratemporal fossa:

- Massetero From zygomatic arch to angle of mandibleo Closes/adducts jaw

- Temporaliso From temporal line to coronoid process

o Closes/adducts jaw- Medial pterygoid

o From medial side of lateral pterygoid plate and maxilla to angle of mandible Angles downward

o Closes jaw- Lateral pterygoid

o From lateral side of lateral pterygoid plate to heads of mandible Straight across

o Protrudes, opens jaw, condylar movementsPharynx:Innervated by CN X except for stylopharyngeusPosterior neck:

- Pharyngeal constrictors: o Superior- from mandible to pharyngeal rapheo Middle- from stylohyoid ligament to pharyngeal rapheo Inferior- from thyroid cartilahe to pharyngeal raphe

- Stylopharyngeus passes from medial side of styloid process to in between superior and middle constrictor

o Travels with Glossopharyngeal nerve (CN IX)- Stylohyoid passes from lateral side of styloid process-> splits to allow passage of

intermediate tendon of digastricRemove constrictor muscles:

- Salpingopharyngeus from auditory tube to palatopharyngeus muscle- Palatopharyngeus in palate- Laryngeal muscles around larynx- Esophageal muscles- Stylohyoid ligament from styloid process to hyoid bone- Hyoglossus

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Tongue Muscles

- Extrinsic- change position of tongue, all CN XII except for palatoglossus (CN X)o Genioglossus- attaches to mental spine, depresses tongueo Hyloglossus- attaches to hyoid bone, depresses and retrudes tongueo Styloglossus- attaches to styloid process, retrudes and curls tongueo Palatoglossus- attaches to soft palate, elevates tongue

Innervated by CN X- Intrinsic

o Attached to tongueo Change tongue shapeo Four muscles: superior and inferior, longitudinal, transverse, vertical

3 parts of pharynx1. Nasopharynx- above soft palate, communicates with nasal cavity through choanae2. Oropharynx- between soft palate and epiglottis3. Laryngopharynx- posterior to larynx, communicates with larynx through inlet of

larynx

Palate

Ring of Tonsils: Waldeyer’s RingPharyngeal, tubal, palatine, lingual, lateral band of tonsilInflammation affects respiration, feeding, speech

Eye- Levator palpabrae superioris

o Elevates upper eyelido CN III- Occulomotor

- Superior rectuso Elevates, adducts, rotates mediallyo CN III- Occulomotor

- Inferior rectuso Depresses, adducts, rotates laterallyo CN III- Occulomotor

- Medial rectuso Adductso CN III- Occulomotor

- Lateral rectuso Abductso CN VI- Abducent

- Superior obliqueo Depresses, abducts, rotates mediallyo CN IV- Trochlear

Also in trochlear notch- Inferior oblique

o Elevates, abducts, rotates laterallyo CN III- Occulomotor

- SO4LR6R3

- CN V1- Opthalmico Nasociliary (anterior and posterior ethmoidal)

Anterior ethmoidal runs underneath superior obliqueo Frontal nerve

Supraorbital Supratrochlear On top of levator palpabrae superioris

o Lacrimal To lacrimal gland Above lateral rectus and abducent

Lab review Carotid sinus- at bifurcation of common carotid to internal and external carotid

o Baroreceptor (pressure sensor)o CN IX

Carotid body- also at bigurcationo Chemosensoro CN IX and X

Branches of Maxillary Arteryo I’m Deeply Buccled-PIS

Inferior Alveolar, Middle meningeal, Deep temporal, Buccal, Posterior superior alveolar, Infraorbital, Sphenopalatine

Brachial plexus is between anterior and middle scalene muscles Subclavian vein and phrenic nerve in front of anterior scalene From top to bottom: Hyoid bone-> cricothyroid ligament-> thyroid cartilage-

>cricoid cartilage-> thyroid gland (left and right lobe, isthmus in center, pyramidal lobe going upwards), trachea

Ansa cervicaliso Superior portion runs with hypoglossal (CN XII)o Inferior portion loops around carotid sheath

Vagus (CN X)o Superior laryngeal

Internal laryngeal Pierces thyrohyoid membrane Sensory innervation to larynx above vocal cords

o To epiglottis, base of tongue, inf vocal cords External laryngeal

To cricothyroid Motor innervation to tense vocal cords

o Recurrent laryngeal Sensory to larynx below vocal cords Enter larynx underneath inferior constrictor muscles

Hypoglossal (CN XII) is more lateral to superior laryngeal nerve Stylohyoid muscle warps around tendon of posterior digastric Infratemporal fossa

o Inferior alveolar nerve and artery to mandibular foramen Nerve to mylohyoid off of inferior alveolar

o Lingual nerve Chorda tympani joins

o Auriculotemporal nerve wraps around middle meningeal artery AT going lateral to medial, MM going up and down

o Buccal branch of V3 (deep)- sensory Different than buccal nerve of VII (superficial)- motor to muscles of facial

expression Layers of Pharynx

o 1. Buccopharyngeal fascia (on outside) Pharyngeal plexus (CN IX and X) Retropharyngeal space in medial neck- site of infection

o 2. Constrictors: Superior, Middle, Inferior Innervated by pharyngeal plexus

o 3. Longitudinal muscles Stylopharyngeus- btwn superior and middle constrictors (CN IX)

runs with CN IX Glossopharyngeal Palatopharyngeus – in mouth (CN X) Salpingopharyngeus- in nasopharynx (CN X)

o 4. Pharyngobasilar fasciao 5. Mucosa

CN IX Glossopharyngealo Runs with stylopharyngeus and also to tonsillar bed between palatoglossal and

palatopharyngeal arches Superior orbital fissure

o CN III, IV, V1, VI Optic canal

o CN II and ophthalmic artery Jugular Foramen

o CN IX, X, XI and internal jugular vein Hypoglossal Canal

o CN XII on side of foramen magnum Internal acoustic meatus

o CN VII, VIII Sphenopalatine foramen

o Sphenopalatine artery and nasopalatine nerves to nasal septum Sinuses

o Superior sagittal, straight sinus and occipital sinus drain to confluence of sinuses Confluence of sinuses drain to transverse sinuses

o Inferior sagittal drains to straight sinuso Cavernous sinus on the side of sella turcica (part of sphenoid bone that holds

hypophysial fossa with hypophysis) Drain to superior and inferior petrosal sinus towards back of head

Superior petrosal to transverse sinus Inferior petrosal to internal jugular vein

o Transverse sinus drains downwards to sigmoid sinuso Sigmoid sinus drains to internal jugular vein

Maxilla

o Incisive foramen with nasopalatine nerve (running from sphenopalatine foramen to nasal septum to palate)

o Greater and lesser foramina with nerveso Palatine bone and palatine processo Pterygopalatine ganglion near spehnopalatine foramen

Gives off greater (in front) and lesser (in back) palatine nerves Descending palatine artery in the middle-> gives off greater and lesser

palatine arteries Seen in medial dissection of nasal cavity

Erb’s Point/Nerve Point In necko Come in front of sternocleidomastoido Great auricular going upwards to earo Transverse cervical nerve going medially to front of necko Lesser occipital going to back of heado Supraclavicular nerves going downwards to clavicleo Causes waiter’s hand- Erb’s palsy

CN XI- Accessory Nerve

o Posterior to sternocleidomastoid

o Innervated by facial nerve CN VII

Geniohyoid attaches to mental spine (genial tubercle)- CN XIIo Underneath mylohyoid (nerve to mylohyoid from inf alveolar from V3)

Underneath anterior digastric (CN V3) Between hyoglossus and mylohyoid forms a sling for sublingual gland

o Submandibular duct runs straight from gland to sublingual caruncleo Lingual of V3 nerve runs underneath duct and dives into tongue

Palatoglossus (CN X) runs upward, styloglossus (CN XII) runs posteriorly Salpingopharyngeus in nasopharynx under auditory tube Lingual artery to back of tongue (larger)

o With hypoglossus nerve (CN XII)- gives branches to back of tongue Pharyngeal tonsils above auditory tube

o Torus tuberis is the cartilage on top of auditory tube Levator veli palatine (CN X) and tensor veli palitini (more anterior) (CN V3)